Paging is a function which enables a core network to page a user equipment device for terminating service requests.
Paging a user equipment device which is in an IDLE mode or a UTRAN Registration-Area Paging Channel Mode (URA-PCH mode) is typically performed with a paging message known as a PAGING TYPE 1 message (as defined in the 3rd Generation Partnership Project, technical specification 3GPP TS 25.331), which is transferred on a logical channel known as the paging control channel (PCCH). A paging message such as a PAGING TYPE 1 message can carry a number of paging records addressing different user equipment devices.
There is a physical capacity limit for a paging channel (PCH) transport channel. As such, there is a limited number of paging messages that can be sent each second. If the limit is reached, new paging messages cannot be scheduled and must be discarded instead, or delayed as shown in U.S. Pat. No. 6,731,944.
Existing mechanisms for scheduling paging messages on a paging channel are based on the principle of trying to increase the probability of a paging message reaching the intended user equipment device, for example to increase the probability of a user equipment device receiving a paging message in the event of radio disturbance.
The existing solution in a wireless regional area network (WRAN) is to schedule each paging record multiple times on the paging channel. The reason for this is to increase the probability that the user equipment device will hear the page. If the first scheduled paging attempt is not received by the user equipment device, for example due to short disturbance in radio conditions, there is a good chance that the user equipment device will hear the repetition paging attempt without a problem.
However, this ever increasing trend in the amount of paging attempts that a WRAN shall handle, by scheduling paging attempts multiple times for a UE, causes even further capacity problems on the paging channel. As such, there is no capacity to schedule paging attempts for other user equipment devices.
This increase can be avoided by reducing the size of the paging area, but at the cost of an increased need to provide location updates, i.e. because a user moves between different paging areas more frequently.
Furthermore, a high inflow of Radio Access Network Application Part (RANAP) paging messages from a core network may trigger overload in the paging message flow within a radio network controller. RANAP paging messages are specified in 3GPP TS 25.413. The overload in the paging message flow in the radio network controller can be triggered either during the internal distribution phase of the paging message in a radio network controller, or while scheduling the paging message on the paging channel. In either case, paging messages are discarded unconditionally during overflow, and they are handled on a first come first served basis in the radio network controller.